Removal of phosphates and Cr(VI)from water by iron lanthanum bimetallic MOF
A magnetic Fe/La bimetallic MOF(Fe/La-MOF)material,which prepared by a rapid and efficient electrodeposition method,was applied for phosphates and Cr(VI)removal from water.The results indicated that the individual phosphate or Cr(VI)removal rates could reach over 94%for phosphate(initial concentration of 100mg P/L)or 95%for Cr(VI)(initial concentration of 20mg Cr/L)after 120 min reaction under the conditions of a equimolar ratio of Fe to La,Fe/La-MOF dosages of 1g/L(for phosphate)or 2.5g/L(for Cr(VI))and ranges of pH 2～7(for phosphate)or pH 2～11(for Cr(VI)),respectively.The Langmuir isotherm model could fit the adsorption of phosphate or Cr(VI)by Fe/La-MOF well,with theoretical maximum adsorption capacities of 350.4mg P/g and 33.4mg Cr/g,respectively.The adsorption behavior of phosphate or Cr(VI)by Fe/La-MOF could be better described by pseudo-second-order kinetics model,implying that the process is mainly chemical adsorption.Characterization results of XPS,XRD and FTIR revealed that ligand exchange between phosphate or Cr(VI)anions and Fe/La-OH could be the main removal mechanism.Furthermore,the magnetic Fe/La-MOF would be easy separated with good stability through 3 cycles of use.The good performances on simultaneous removal of phosphate and Cr(VI)were also exhibited with the removal rates of 100%for phosphate(initial concentration of 25mg P/L)and 92.2%for Cr(VI)(initial concentration of 20mg Cr/L)after 120min reaction under a neutral pH and Fe/La-MOF dosage of 2.5g/L.In general,Fe/La-MOF is a highly efficient adsorbent for removing phosphate or Cr(VI)with greater adsorption capacities and good stability in a wider pH range.
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